A method for the isolation of a homogenous preparation of CNS myelin proteolipid protein (PLP) has been developed in this laboratory. We are currently engaged in determining the N-terminal amino acid sequence of the native, reduced, oxidized or carboxymethylated PLP by direct Edman degradation. Cyanogen bromide fragments and tryptic peptide maps will be prepared, the peptides will be purified either by gel filtration or ion exchange chromatography, and the amino acid sequence of these polypeptides will be unravelled by Edman degradation by the use of an automatic amino acid sequence. We have produced monospecific precipating antibodies to rat brain myelin PLP in both rabbit and goat. Using immunohistochemistry we are studying the appearance of myelin specific PLP in developing rat and bovine brain and light and electron microscopes. Such as approach will enable us to determine: a) the sequential appearance of PLP in discrete anatomical areas of the brain during development, and b) how this protein becomes an integral part of myelin membrane after its synthesis in oligodendrocytes.